Cluster randomised trials: time for improvement

Cluster randomised trials.

Although randomised controlled trials are the reference methodology to assess the effects of therapeutic interventions, for interventions that naturally occur in groups of individuals random allocation of participants may be inappropriate. In these cases, the unit of random allocation may be the group or cluster, rather than the individual. Clinical trials that randomly allocate groups or clust...

Cluster randomised trials : Methodological and ethical considerations

How to design efficient cluster randomised trials

Cluster randomised trials have diminishing returns in power and precision as cluster size increases. Making the cluster a lot larger while keeping the number of clusters fixed might yield only a very small increase in power and precision, owing to the intracluster correlation. Identifying the point at which observations start making a negligible contribution to the power or precision of the stu...

CONSORT statement: extension to cluster randomised trials.

Preventing Bias in Cluster Randomised Trials

In randomised trials, internal validity is defined as ‘‘the extent to which the design and conduct of a study are likely to have prevented bias’’ [1,2]. In conducting such trials, trialists try to prevent selection bias through randomisation and allocation concealment (defined as ‘‘the process used to ensure that the person deciding to enter a participant into a randomised controlled trial does...